Why do we care about making a distinction?
It is generally good when the words that we use have the same meaning
for different people. If we are trying to share information, such as
what materials might catch a spark from flint and steel, it is important
to know which flint and steel was used. A lot of primitive skills come
as a result of many hours or days of searching, research and/or skills
development. To say that a particular material has a certain property
could take one down a path of wasted time and effort. I have personally
been misled many times, hence my motivation for trying to provide a bit
of clarity. (I.e one can light “almost anything” with Ferrocerium. There
are very very few things that will readily accept a spark from
traditional flint and steel.

Traditional Flint and Steel

In the traditional flint and steel technique, a piece of hardened
steel is struck against a piece of flint. Some people may reverse this
and strike the steel with the flint. In either case, what takes place is
this:

The sharp edge of the flint cuts off a tiny piece of steel.

This cutting action generates heat.

With enough heat, the fleck of steel “ignites.” i.e. combines
with oxygen in the atmosphere and “burns.” We see this as a spark.

For step 1, it is important to note that the flint remains intact.
The steel is consumed. Of course, over time, the flint will become dull,
but its action is strictly that of a cutting tool. Flint is not the only
material that can be used as a cutting tool. Other hard rocks, such a
jasper, quartz etc. also work well.

To better visualize step 2, recall what happens when you saw or drill
a piece of steel. It gets hot. If we put enough energy into the cutting
process, the “cuttings” become very hot, in fact red hot.

What if we consider steps 1 and 2 together? Can we substitute the
flint with a cutting tool? The answer is yes! If you have access to a
piece of carbide (very hard tool steel,) try striking you traditional
“steel striker” against the carbide. You get sparks from steel on steel!

For step 3, we need to understand that steel can and does burn. To
make this more approachable, try “lighting” a ball of “steel wool.” You
can ignite the steel wool with a match, or use it like tinder with
almost any spark generating device*, or use a
battery. Once the steel wool
has “caught,” it burns. Not with a flame, but sure enough you can watch
the fibers get consumed. Another example of this is cutting steel with
an oxy-acetylene torch. The technique here is to heat a small spot of
steel with a hot flame. Once the steel is red hot, the original flame is
no longer required. A cutting torch has a special button which releases
a high pressure stream of oxygen. The hot steel then burns intensely.
Using this technique, one can cut through a 2”x4” piece of steel in a
half minute of so.
(* Note that when a “spark generating device” is mentioned, there is
another trap that we can fall into. The term “spark” also has many
definitions. A spark from static electricity, a piezoelectric spark, a
spark from short-circuiting a battery, and a spark from flint and steel
are again all radically different.)

The bottom line to all of this is that if you get a piece of steel
hot enough, and it is in the presence of oxygen, then it will burn. By
the way, steel “burns” at around 1370°C. A rather high temperature,
hence the need for just the right ingredients to make this method
workable.

I hope that the above description explains the basic mechanics of
traditional flint and steel. While on this topic, it would be useful to
make a few comments on the steel itself. For a good steel “striker” one
needs very hard steel. If the steel is too soft, then it is too easy to
slice off tiny flecks of steel and not enough heat is generated for
combustion. Typically people use pieces of old files, pieces of springs
from car suspensions etc. If you are buying steel for a striker, then
you need to purchase something with a high carbon content. Steels are
typically graded on their carbon content. A 1018 steel has .18% carbon,
while a 1095 steel has .95% carbon. A 1018 steel will not spark. 1095
sparks well. The more carbon, the better the spark. It is not the carbon
which is “burning,” but rather the addition of the carbon makes a harder
steel.

Ferrocerium or “Metal-Matches”

In the era of non-disposable lighters, one might have heard, “I need
a new flint for my lighter.” Or even with disposable lighters, one might
hear, “The flint just when on my lighter.”
Somewhere here things got really mixed up and life hasn’t been the same
since! (At least for those of us who play with fire.)

The “flint” that one puts in a lighter is completely different from
the rock that we call flint.
The “flint” that one puts in a lighter is completely different from the
rock that we call flint.
The “flint” that one puts in a lighter is completely different from the
rock that we call flint.

Please re-read the above sentence a few times.

OK, so if it’s not rock, what is it?
The “flint” in a lighter is more accurately called FERROCERIUM. I guess
“flint” is a lot easier to say, hence the mess that we’re in!

So what the heck is FERROCERIUM?
Glad you asked – but you may be sorry!
Ferrocerium is a mixture of Mischmetal, Iron Oxide, and Magnesium Oxide.

Misch what? Mischmetal. Remember that for the next time you want to
be avoided at a cocktail party. To not even get invited to the next one,
read on….

Mischmetal is literally a “mixture” of metals. Carl Auer Welsbach,
(Baron von Welsbach) discovered this mixture in 1903 – hence the use of
the German “Misch.” For your next trivia game, von Welsbach also
invented mantles for gas lanterns.

Mischmetal is a mixture of Rare Earth Elements: Cerium, Lanthanum,
Neodymium, and Praseodymium. There are the Group 1 Lanthides which are
distinct from the other Lanthides by their low melting points, but high
boiling points. They are called Rare Earth Elements because when first
isolated they were believe to be rare. We now know them to be as common
at Tin. Check your cupboards for tin cans and you get the picture. Bonus
points if you rebutted with the fact that tin cans aren’t actually made
of tin – but that is yet another story about how messed up our
vocabulary is. Oh yes, we were talking about fire weren’t we….

It turns out that separating the Group 1 Lanthides is about as easy
as putting scrambled eggs back in their shells, so for non-critical
roles (read fire-starting) no-one bothers to perform much refinement,
hence using the misch or mixture. When all is said and done, this is one
(pyrophoric) recipe:

Mischmetal
Cerium: 50%
Lanthanum 24%
Neodymium 3%
Praseodymium 3%

Mischmetal is usually about 50% Cerium. The most interesting thing
about Cerium (when your fingers are freezing in the forest) is that it
has an ignition temperature in the range of 150°C to 180°C. Remember
water boils at 100°C. So, at less than twice that temperature, we can
get Cerium to ignite – how cool is that! The other Group 1 Lanthides
behave similarly, and it is claimed that leaving them around in the
mixture drops the overall ignition temperature of Mischmetal by a few
tens of degrees – even better! Compared to carbon steel, Mischmetal
ignites at a much lower temperature than steel. This means that it takes
far less “work” to get a spark from Mischmetal than from steel. And this
means we get a lot more sparks for less work with this
method when compared to flint and steel. Based on the ignition
temperatures, one would be tempted to say that steel burns at about 10
times the temperature of Mischmetal. Following the pattern of this
write-up, you would of course not be surprised to hear that the previous
statement may or may not be true depending on how you measure
temperature – whether you use Fahrenheit, Celsius, Rankin, or Kelvin.
Sigh…. yet another topic to think about. Oh yes, we were talking about
fire, weren’t we…

Again, to get a better feel for some of this chemistry, the next time
you scrap some sparks from a metal match, have a look at the area that
was scraped. Nice and shiny isn’t it.
Now have a look at the rest of the metal match – it is very dark. But,
haven’t you scraped that thing before –and had the same metallic shine
left behind? Here is another key point – which is coupled to the burning
point for cerium (and the other Group 1 Lanthides) - rapid oxidation.
Check back on that metal-match now and then and track how long it takes
to return to its black or oxidized state.

As it turns out, Mischmetal is pretty soft. The usual metallurgical
solution to this sort of problem is to add some alloying compounds. If
we mix up the following:

Mischmetal 78%
Iron Oxide 20%
Magnesium Oxide 2%

Tada! We end up with Ferrocerium. You may now unglaze your eyes! We
have finally arrived at the “stuff” that we find in lighters,
metal-matches, Blast-Matches etc. For completeness, I did a few tests on
Ferrocerium shavings. My experiments showed that they would ignite at
around 210°C. Again, in honor of the Baron, some people also call
Ferrocerium Auermetall.

Let’s review how we use a “stick” of Ferrocerium. Often if you buy a
Ferrocerium based fire-starter, there will be some sort of “steel”
included which is used to scrap sparks from the stick. This is another
element which makes one think this technique is “flint and steel.” In
reality, given the low ignition point of Ferrocerium, almost anything
can be used to generate sparks. In this case we want something that is
just hard enough to be able to scrape a shaving from the Ferrocerium
(“flint.”) This could be a knife blade, a piece of rock, a piece of
glass. Anything that is somewhat sharp and somewhat hard will do the
trick. Give it a try. Remember, you only need to generate a few hundred
degrees instead of more than a thousand. (Those are Celsius degrees.)

Here is a challenge for you. I like to carry just a raw piece of
Ferrocerium with me. It is convenient to drill a hole in one end and
loop some string through the hole. This helps to keep the Ferrocerium
from getting lost, and also provides for a secure grip. Most, if not
all, pieces of Ferrocerium don’t have a hole at one end. Just try
drilling a hole in one end without generating any sparks. It doesn’t
matter how much coolant, or how slowly I drill the Ferrocerium, I always
end up getting sparks. Contrast this to what happens when you drill a
piece of steel.

Another interesting thing to note is that some Ferrocerium sticks
come attached to a block of magnesium. The idea is to create a pile of
magnesium shavings on one’s tinder, and then to light this using
“sparks” from the Ferrocerium. From what we have discussed, it would
also be reasonable to believe that one could slowly and carefully scrape
the Ferrocerium and to create a pile of shavings. A few sparks would set
this pile alight. This of course is true – and a useful technique to
know when one is using less that perfect tinder (and one doesn’t have a
block of magnesium!) By the way, the ignition point for magnesium is
473°C. This of course teaches us something else. While the ignition
temperature of Ferrocerium is around 200°C, it clearly burns at a much
higher temperature – at least 473°C. The temperature of burning
Magnesium is up around 2200°C! So there is a valuable “bootstrapping”
effect when one lights Magnesium shavings with Ferrocerium.

The Bottom Line

If you skipped over the pedantic part, this is where it all comes
together.

When someone says, I started a fire with “flint and steel”
what the heck are they talking about?

Did they use:

“Flint and steel” to mean the “rock we call flint” and hardened
steel – both of which are involved in a process where the steel is
“cut” and as a result heated and subsequently oxidized to make a
spark. (Remember that the “flint” is not needed in this scenario,
just something very hard and sharp.)

Or, did they use:

“Flint and steel” to mean the mixture we call Ferrocerium
(flint) which is oxidized as a result of the “steel” mechanically
removing and heating the Ferrocerium to the point where it burns.
(Remember that the “steel” is not needed in this scenario, just
something sharp.)

In one case, we are generating a spark from the steel, and in the
other case, we are generating a spark from the “flint”.

After all of this chemistry, physics and history, one might rethink
the typical categorization of these fire-making methods as primitive!
This brings us to generating sparks by just striking two rocks
together... Another topic for another day…

I know that there are probably causes more worthy in this world, but
the next time that someone casually states that they used “flint and
steel” to start a fire, please set the record straight.

As with anything on the internet, what I have written could be quite
wrong or misleading. This was not my intention. Verify any of the facts,
data, inferences, or suggestions if the conclusions are in any way
important to you. Please help me out my letting me know where you might
disagree or where I have erred.